Method of making crucibles



Jan. 19,1926. l 1,570,064

' A. J. JACKMAN METHOD 'oF MAKING-CRUCIBLES F11ed March 18, 1925Patented r`lan. 19, 1926i.

. 1,570,064 PATENT OFFICE.

ARTHUR JOHN JACKMAN, or Former HILLS BoaOUGH, rENNsYLvANIA, AssIGNon 'rovEsUVIUs o nUoIBLE COMPANY, or swrssvann,y IENNSYLVANIA, A CORPORA- TIONVOF IPEN'NSYLVANIA.l

' METHODOF'MAKLNGYORUOIBLES.

Application led March 18,1925.y Serial No. 16,344.

To all whom.` t mag/"conectan f i Be it known thatzI, ARTHUR JOHN. JACK-MAN, a citizen of the United States, residing at Forest Hills Borough,county of Allegheny, and State of Pennsylvania,.have invented a new anduseful Improvement in Methods of Making Crucibles, of which thefollowing is a full, clear, and exact description. Y

The present invention pertains to a method of making Crucibles and isparticularly adapted to the manufacture ofgraphite crucibles such as areused in the manufacture of steel.

Metal melting crucibles, as for example, graphite c-rucibles usedk insteelv manufacture, are subjected to internal erosion of three principalsorts; namely, the oxidation of thegraphite by available oxygen in thebath, the absorption of carbon from the Crucible by the metal, and thefluxing action of the slag on the material used to bond the crucible.This last constitutes a very destructive localized attack.

I-Ieretofore it has been common practice to line such crucibles withvarious materials, possessing greater resistance than the body of theCrucible to the corrosive action of the slag, to obtain greater life forthe crucibles Or to obtain carbon free metal. Complete linings have beenfound unsatisfactory, however, because of the irregularity of the amountof carbon absorbed by the metal when the lining becomes cracked, acircumstance which eventually obtains. Y

Thek repair of eroded Crucibles has also been tried. The repairs havebeen made by filling the crack or groove formed in the Crucible with amaterial similar to that of which the Crucible or Crucible lining ismade. This procedure has not always proved effective because the firstheat of service renders a crucible hard burned and vitreous, andmaterial subsequentlyl filled into cracks or grooves in the surface ofsuch a Crucible cannot become firmly bonded thereto. In addition tothis, the usual practice in Crucible steel furnace operation is tocharge the Crucibles while yet hot from theY previous heat and put themback into the furnace. Under suchv operating Condltions patching isimpracticable.

Avoiding these obJections andy producing adcrucible of longer `life thanthose hitherto manufactured, my invention provides for incorporatingl aprotecting ring of slag resisting material inthe interior'of theCrucible-'at the time it is manufactured.v Thus I am able to produce acrucible presenting a monolithic body of graphitic composition to thebulk 4of the metal, at the same time presenting to the slag a protectivering of a composition best vsuited to resist the fluxing action of thesame. Y .Y f v In makingY these protective rings I preferably employsuch materials as chromite,

sillimanite, zirconia, spinel,- Zircon, `for compositions containing oneor more of. these ingredients. It will be understood, however, that I amnot limited/to these materials, since it is obvious that rany highly.refractory substance that is neutral; and resistant to the iluxingaction of the slags encountered will serve my purpose.. Imay also employgraphite-.in thesey rings in order that the thermal and physicalrproportions of the rings will more closely approximate those of theCrucible body. These protecting rings may be bonded with any suitablebonding material, such as those now well known in the art. l,

In the accompanying-drawings, illustrating the present preferredembodiment. .of the invention- Y Figure 1 is a vertical section of acrucible having a ring Cut in the inner surface in the vicinity of theslag line; y

Figure 2 is a cross sectional view of a Crucible provided with aretaining groove having the side portions undercut.; l

Figure 3 is a sectional view to enlarged scale, illustrating a portionof the Crucible shown in Figure 2 with the protecting material in place;

Figure 4 illustrates a slag resisting ring similar to that shown inFigure 3 but provided with a protective coating to prevent abrasion ofthe inlay until the crucible is hard burned.

Referring first to Figure l, there is shown a Crucible 2, having anannular groove 3 whosefside walls 4 are cut substantially perpendicularto the inner surface ofthe crucible wall. The groove 3 is preferably cutwhile the Crucible is soft and lunburned. `I have found that the depthof this groove 3 should not be greater than two-thirds the thickness ofthe CrucibleJ` wall. Greater depth of cut adds no mechanical strength tothe finished vslag resisting ring and may seriously weaken the crucible.

Figure 2 illustrates a crucible EZa having a retaining groove 5 cuttherein. This groove Vhas sloping'sides 6 which effectively retain thematerial Y packed in the groove, as better shown in Figure 3. Inpractice it is found that the width of such a groove need not exceedeight inches, as the depth of the slags encountered does not warrant it.It Awill be understood, however, that this dimension -is not to beconstrued asa limit.

In constructing such a crucible as shown in fFigure -3 it is desirablethat the slag resisting material 7 should have contact with the 'sidewalls 6 and the inner wall 8 to insure the material 7 being firmly heldin place. It is obvious that if the material i' has a smaller shrinkagethan the crucible wall 2 it will be crushed during drying or firing. Toobviate this diculty, I prefer to form the crucible body and permit itto partially dry before-the slag ring is molded into the groove. Whenthis is done the differential in shrinkage between the crucible body 2and the slag resisting material 7 is reduced to practically nothing.

Certain of the desirable slag resisting materials, such as water groundzirconia without added bonding material, do not possess much physicalstrength or resistance to abrasion until they have been sintered athigher temperatures than those usually employed in the manufacture ofgraphite crucibles. When itis necessary to depend upon the heat of thesteel furnace to give such materials a final firing, I provide forcoa-ting the exposed portion of the .ring with a ceramic composition toprotect it from abrasion. In Figure 4 such a composition 9 is shownextending above and below the slag resisting material 7, making contactwith the crucible body `2. For such a composition.9, I preferably employa mix sufficiently similar to that used in the Crucible body 2 that agood'bondis secured therewith above and'below the slag ring, thusinsuring protection of the slag ring until the Crucible has been hardburned. rIhe protective coating 9 is soon destroyed during the early useof 'the 'crucible and the slag resisting ring performs its function asabove described.

While 'I have described the preferred vein-- bodiment of the invention`it will be understood that the drawings do not define the limits of theinvention, which may be otherwise embodied within the scope of thefollowing claims.

I claim:

1. As an article of manufacture, a crucible for a melting operationwherein a is formed, having a portion adapted to contact with the slagand made froma material more resistant than the body of the Crucible tothe corrosive laction of the slag, substantially as described.

2. As an article of manufacture, a crucible for a metal meltingoperation wherein slag is formed, having a graphitic'body portionadapted to 'Contact with the bulk of the metal and having 'a portionadapted to contact with theslag and made from a material more resistantthan the said body portion to the corrosive laction of the slag,substantially as described.

3. As an article of manufacture, a 'crucible 4foran'operation whereinslag is formed, having an inlay of refractory material more resistantthan `the body -of the Crucible to the corrosive actionof the slag,substantially as described.

4. As `an article lof manufacture, a crucible for an'operation whereinslag is formed, comprising a body portion of refractory material andhaving an interior ring of inaterial `more'resistant to the fche'micalattack of the slag than the said body yportion incorporated therein atsuch kportions as normally contact with the slag, substantially asdescribed.

5. `Asan'article of manufacture, a crucible for an operation whereinslag is formed, comprising a body portion of :graphitic material andhaving an interior ring of material more resistant to the chemicalattack of the slag than 'the said body portion incorporated therein atsuch portions `as vnormallycontact with the slag, substantiallyasdescribed.

6. vAsan article `of manufacture, a crucible for an operationwhereinslag is formed, comprisinga graphite body, means for Iprotectingthe said body lportion .from'the corrosive action 'of the slagcomprising an inlay of materialmore resistant to the chemical attack-ofthe sla'gthan the body portion, and means for protectingthe inlaidmaterial from injury prior to hard burning, comprising a 'veneer ofrefractory material `placed thereover, substantially fas described.

7. Asan article of manufacture, a crucible `for an operation whereinslag is formed, comprising a graphite body, means -for lprotecting thesaid body portion lfrom the corrosive actionof the slag comprising aninlay of material 'more resistantlto the chemical attack vof the slagthan thebody portion, and means forprotecting the inlaid'material frominjury Vprior to hard burning, comprising a veneerof refractory materialoverburned at 'a lrela'tively lower temperature than required for hardburning the inlaid material, substantially as described.

v8. As 'an article of manufacture, a crucible for an operation whereinslag is formed, having a graphitic body portion, meansfor protecting thebody portion fiom the corrosive action ofthe slag comprising an yannularringv of refractory material, more resistant to the attack of the slagthan the body portion, inlaid in the body portion at such portionsthereof as are normally in Contact with the slag, and means forprotecting the said inlaid material from injury prior to hard burningcomprising a thin layer of material laced over the said inlaid materialand Bonded to the said body portion, substantially as described.

9. The method of making a Crucible for an operation wherein slag isolmed Comprising forming a body portion having a groove therein at theslag Zone, and thereafter packing the groove with material moreresistant than the body portion to the Corrosive action of the slag,substantially as described. f

l0. The method of making a Crucible for an operation wherein slag isformed comprising forming a body portion having an annular groove, WhoseWidth is greater aty the bottom thereof than at the top, at the regionnormally in Contact with the slag, thereafter packing said groove Withmaterial more resistant to the chemical attack of the slag than the bodyportion, and placing thereover a layerl of material adapted to protectthe inlaid material from injury prior to hard burning, substantially asdescribed.

l1. The method of making a graphite crucible for an operation whereinslag is 'formed comprising forming a body portion having an annulargroove, Whose Width is greater' at the bottom thereof than at the top,at the region normally in contact with the slag, thereafter packing saidgroove With material more resistant to the chemical attack of the slagthan the body portion, placing thereover a layer of material adapted toprotect the inlaid material from injury prior to hard burning,and tiringthe crucible so made, substantially as described.

12. The method of incorporating a slag resisting portion having arelatively lovvl d ing shrinkage into a crucible having a re ativelyhigher drying shrinkage comprisrelatively higher drying shrinkagecomprisj ing forming the Crucible to a desired shape and drying the sameuntil a predetermined proportion of the total shrinkage has taken lace,thereafter introducing the slag resistrlng portion'into the saidCrucible, and placing thereover a material adapted to protect the slagresisting portion from injury prior to hard burning, substantially asdescribed.

lll. The method of incorporating a slag resisting ring having arelatively loW drying shrinkage into a graphite Crucible having arelatively higher drying shrinkage comprising forming the graphitecrucible to a'desired shape and drying the same until a predeterminedproportion of the total shrinkage has taken place, and thereafterintroducing the slag resisting ring into the said graphite Crucible,substantially as described.

15. The method of incorporating a slag resisting ring having arelatively 10W drying shrinkage into a graphite crucible having arelatively higher drying shrinkage comprising forming the crucible to adesired shape and drying the same until a predetermined proportion ofthe total shrinkage has taken place, thereafter introducing the slagresisting ring into the said Crucible, and placing thereover a materialadapted to protect the slag resisting ring from injury prior to hardburning, substantially as described.

In testimony whereof I have hereunto set my hand.

ARTHUR JOHN JACKMAN.

